Treatment of oil productive sands



Patented' Feb. 22, 1944 UNITED STATES 2,342,424 I TREATMENT or on.PRODUCTIVE SANDS No Drawing. Original application June 28, 1938,

Serial No. 216,284. Divided and this application April 11, 1939, SerialNo. 267,348

1 Claim.

. This invention relates to the treatment of oil or gas-productive sandsin order to increase the flow of oil or gas into the well and is adivision of my co-pending application Serial No. 216,284, filed June 28,1938. The invention particularly relates to a method for increasing'thepermeability of producing formations.

In the drilling of oil and gas wells, particularly by rotary toolmethods, it is conventional to employ a drilling fluid to aid in thedrilling operation. The fluid which is generally an aqueous suspensionof solid matter such as clay, bentonite or other solid material 01'even' plain water is pumped down through the drill stem, circulatesaround the tool or drill bit employed for the .drilling operation andrises between the drill stem and the wall of the hole to the surface ofthe well. The purpose for the use of the drilling fluid is to carry tothe surface of the hole the cuttings made by the drill bit. However, thedrilling fluid also serves to lubricate and cool the drill bit and byits weight and pressure prevents the well from blowing in prematurely.Since the prevention of the entrance into the boreholeof the highpressurefluids in the penetrated 'formation, such as oil or gas, isaccomplished by the hydrostatic head of the drilling fluid or mud, it isdesirable that this fluid should have a maximum density compatible withits other desirable characteristics. For this purpose, it isconventional to add to the. drilling fluid such weighting in the porespaces of formations containing oil and gas which has the same effect inpreventing the flow of oil and gas to the well.

It is an object of our invention to treat oil and gas-producing sands orformations for the purpose of removing obstacles which prevent the flowof oil and gas into the well. A particular object of our invention is totreat the producing sands with a substance which is adapted to reducethe adhesion tension of the water for the sands. Other objects,advantages and features of our invention will be better understood fromthe following description of our invention.

We have discovered that if the sands are treated with a substance whichwill dissolve or emulsify the water present in the producing sands andwhich will lower the surface tension forces holding the water in thesand. such material containing the water in solution will be morereadily expelled from the sand into the borehole by the flow of the oiland gas into the well.

the water from the drilling fluid and the connate Thus,

- zones of a material that will dissolve or emulsify materials asbarytes;.nematite and finely divided iron.

The existence of a greater pressure due to the hydrostatic head of thedrilling fluid in the borehole than that in the formation, however,results ordinarily in the penetration and loss to the formation ,of aquantity of the aqueous portion of the drilling fluid. This loss ofwater into the oil and gas productive strata seriously impairs theproductivity of thewell particularly in low pressure zones since it hasa higher adhesive tension than oil for the sand in the productive zoneand therefore the water will displace the oil film from the sand grainsand capillaries. In other words, the sand has a greater attraction forthe water than for the oil, resulting in adsorption of water on thesurface of the sand thereby reducing the porosity or permeability of thesand surrounding the borehole. Consequently, water that finds its wayinto and is present in a sand formation will remain in the finercapillary spaces within the structure interfering greatly withthesubsequent production of oil from the well. Furthermore, connatewater is also present frequently water that may be pres nt in the sandand that will be subsequently readil driven from the sand into the weltby the 'production of oil-and gas.

' The materials which are capable of accomplishing the desired resultare either of the type that dissolve water but would not be-dissolved inoil or of the type capable of being soluble in both oil and water, or ofthe type that will cause the Water to form an emulsion with the oil. Wehave found the following materials suitable for such purpose:

Materials which have mutual solubility for water and oil such as thealcohols, ethyl, methyl, normal and isopropyl; the ethers, such as ethylether and its water soluble homologues; ketones such as acetone, ethyl,methyl and di-ethyl ketone and their Water soluble homologues; andmixtures of alcohols and ethers and/or ketones;

phenols such as phenol and cresol surface active agents such as estersof sulfonated dicarboxylic acids and water-soluble salts thereof;sulfonated alcohols and sodium and potassium and other water-solublesalts thereof, sulfonated fatty esters and acids and water-soluble saltsthereof; sulfonated mineral oil and water-soluble salts thereof andsoluble salts of alkyl sulphates. An example of an effective surfaceactive agent of the alkyl sulfate type is sodium lauryl sulfate andexamples of the sulfonated fatty acid type by even flowing it down thewell by gravity to the oil sands. The quantity of liquid to be employedfor the operation will, of course, vary with each well, this dependingprimarily on the diameter of the hole at the bottom of the well and onthe thickness of oil-producing sands. In general, however, a sufiicientamount of the liquid is in-' troduced into the well so thata column ofliquid of sufficient height is maintained in the well to force theliquid about four or five feet into the formation by hydrostaticpressure. In' one particular well having an oil-producing formation ofabout 100 feet thick, approximately 2000 gallons of ethyl alcohol wereintroduced into the well which was allowed to flow by gravity down' thewell to the oil sands. The alcohol was allowed to remain at the bottomof the well for approximately 12 hours in order to combine with theconnate water present in the formation after which the liquid in thewell consisting of a mixture of oil, alcohol and water was pumped out ofthe well. The treatment resulted in an increased production.

Another desirable method for effecting the penetration of theadhesion'tension reducing material into the above mentioned formationthe required distance is to pour the required amount of the materialdown the well and then place the material under a superimposed pressurefor a sufficient period of time to cause the material to penetrate intothe formation and dissolve the water contained in it. The necessarypressure to force the material into the formation may be supplied byforcing a gas, such as airor a fixed hydrocarbon, into the well until asufficient pressure is provided therein. After the material has beenmaintained under the superimposed 'gas pressure for a suflicient periodof time, say -12 to 24 hours, the pressure is released to atmos phericand the liquids in the well are pumped out. If desired, the applicationof gas pressure on the formation may be carried-out inter'm'iltently,that is, the material introduced into the well may be maintained underpressure for a shorter period of time, say for one hour. and then.

the pressure is released for a short period of time to allow thematerial and dissolved or emulsified water to flow back intothe well.The pressure is then reapplied tothe formation for another period oftime and then again released. This alternate imposition and release ofpressure may De repeated a number of times until the operator considersthat-the formation has been treated sufficiently to remove substantiallyall of the ,water present in the producing sands for a distance of fouror five feet from the borehole.

In some cases, it may be necessary to repeat the above operation usingfresh liquid in order to obtain the desired result as the liquidemployed in the previous operation may have become contaminated withconsiderable connate water and other substances before it has penetrateda sufficient distance in the oil- =producing sands to relieve thecapillaries of the sands "sufliciently of connate and other water topermit the oil to flow freely into the well.

While the application of our invention is particularly suited to lowproducing wells in low pressure formations which have been in operationfor a considerable period of time, the invention is equally adapted tothe treatment of new wells; In the treatment of such wells, however,

it is preferable after the well has come into pro duction to allow thewell to produce until the oil production is reduced materially beforethe treatment to remove connate and other water is made.

The-above description of our invention is not to be considered aslimiting 'since many variations may be made by those skilled in the artwithin the scope of the following claim without departing from thespirit of the invention.

We claim: i i

A method of increasing the production of an oilor gas well comprisingintroducing an ester of a sulfonated dicarboxylic acid into the well.

forcing said esterof a sulfonated dicarboxylic.

acid into the interstices of the producing forma- -'tion to contact thedissolved water adsorbed therein and withdrawing said ester-ofdicarboxylic acid together with the-dissolved water" from'said formationand directly thereafter producing said well.

' VJILLIAM M. NEWTON.

PHILIP H.JONES.

